Blends comprising ethylene/methacrylic acid copolymer,polyethylene,and ethylene/vinyl acetate copolymer



United States Patent 3,445,546 BLENDS COMPRISING ETHYLENE/METHACRYL- IC ACID COPOLYMER, POLYETHYLENE, AND ETHYLENE/ VINYL ACETATE COPOLYMER James Thompson Pledger, Jr., Orange, Tex., assignor to 3 ,445,546 6 Patented May 20, 1969 "ice have the acid comonomer distributed in a random manner in each of the molecules of the copolymer. The uniformly random copolymers are preferred in the process of the present invention since they permit completely homogeneous blends in which both components are com- E. I. du Pont de Nemours and Com an Wilmin ton 5 Del., a corporation of Delaware p y, g patible w th each other. Non-un1forn 1 copolymers which Filed 29 19 6, s N 605,624 contain high localized acid concentrations in their molecu- Int. Cl. C08f 29/30, 29/26 lar structure, are not readily compatible and, thus, do not US. Cl. 260-897 4 Claims give rise to optimum values in the properties characteristic 10 of the blends of the present invention. As a result of the significantly higher reactivity of methacrylic acid in ABSTRACT OF THE DISCLOSURE polymerization as compared to ethylene, any polymeriza- Blends of 50-90% ethylene/methacrylic acid random n n which the acid concentration dec ea es during copolymer, 5 to 45% Polyethylene and at least about 5% polymerization will result in non-uniform and non-random ethylene/vinyl acetate that can be melt extruded into 5 P Y F Hence/E116 P Y 'f films. present invention are those obtained in the polymerization environment in which the acid concentration, the ethylene concentration, and the resulting copolymer concentration g g g i figfi 2 E353: g gs hgi g z g iggz" is maintained constant. Constant environment polymeriza- P p y y tion reactors and processes are described in the prior art, copolymers of ethylene and rnethacrylic acid, and copolyfor example See Canadian Patent No 655 298 to mers of ethylene and vinyl acetate. Armitage It IS the Pnmary object of.the Present mventlon to P The ethylene vinyl acetate component of the blend is vlde polyethylen? blends.whlch can be melt extruded. Into likewise preferably a random copolymer. This copolymer 22 5532:: a hlgh degree of toughness wlth 25 can also be produced in a constant environment process.

The blends of the present invention comprise three gg g fig 6 {g gg m Patent 3329- gb lgiifi' o etiglegg gd g ig i z fiz 23% l g gii g The blends of the present invention are prepared by from 2 to 10 mole percent based copolymer of standard techniques. One preferred method comprises dry acid and having a melt index in the range of 1 to 50 blending the components and then extruding the mixture dg /min with (b) about 5 to about 45 Wei rcent through an extruder equipped with a working torpedo in d Pre'ferabl 10 to 20 Wei ht ercent the: the screw which homogenizes the molten polymer comblend of a pyolyethylene havfn densit of 0 910 to ponents of the blend. The resulting blend is then extruded 0 g he and preferabl a dgensit of 8 0 970 and pelletized. The pelletized blend can then be extruded y gmelt index in i range 0 1 20 g /n'lin into film using conventional extrusion equipment and and (c) athleast3 about I51 weight pelracent, but preferably ggz gs g gg igg 5 35 515 132 g g gif z combnot more t an 0 weig t percent, ased on the weight of e tammg about 5 to 15.mO1e percent on the 40 tremely tough and at the same time relatively stiif The 9 g copolynerbof g g al/ld b g 11 lfidex blends may also be employed as a molding resin for the in erangeo a on to g. min. e en 5 ave a melt index in the range of about 15 to 25 dg./min. i ifi Pfg and flixlblhty at tempera The use of polyethylene film as packaging material in g g ii a: zgg g re 6 t the 3 l paikage and P further illustrated in Table I The Ear; i i i Is W i order 9 quahfy for sucih obtained using a two inch extruder and 10 m'l l 6 industrial packaging uses, it is essential that the resin fil f 4 h a 1 at employed for the bags combine toughness with high yield m 16 o 0 me es f h Polymer melt was Strength to prevent bursting and tearing of the bags during heated to 190 C. at the extrusion die and the screw speed shipping and/o1- Storage The most Widely used method was ad usted to deliver about 40 lbs. of polymer per hour. employed to measure film toughness is Elmendorf Tear The film'was taken off at a rate of 12 -P- and blown Strength ASTM D-1424 56 T up to twice the diameter of the die. The resulting film The ethylene-methacrylic acid copolymers employed had film gauge of approximately fivfi mils- All melt index 1n the present invention are preferably uniformly d m values illustrated in the table and otherwise employed copolymers, i.e. copolymers which contain substantially in the description of this invention are based on ASTM- the same acid concentration in all of the molecules and D1238-57-T.

TABLE I Blend Composition Secant E/MAA, E/VA, M lt E Mole Mole Poly- Index Dart Tiia rf gi /iiil percent percent ethylene of Drop,*

A MI Percent VA MI Percent Density MI Blend g./ml. MD TD MD TD 4 22 10 12 6.4 10 .959 6.9 19.5 204 4 22 10 12 6.4 20 .959 6.9 18.9 168 l l 3%.? iii .31 4 22 2o 12 6.4 20 .959 6.9 16.1 144 92 200 37.5 16.2 3.5 36.1 10 12 6.1 10 923 3.7 26.4 275 94 43 11.1 10.8 at is it 21 as a; 95 52 3.5 36.1 20 12 6:1 30 I923 317 1518 2i3 iiIg *ASTM D170962T Method A using a 2" diameter dart and a 26" drop.

The blend compositions of the present invention are primarily employed in the manufacture of film which iS used in industrial packaging applications, particularly in the bagging of chemicals such as fertilizer. The inertness of the ethylene polymers combined with the aboveoutlined mechanical properties makes these materials particularly suitable for such purposes. However, it is to be understood that the utility of the blends of the present invention is not limited to such applications, and the blends can be employed in all applications developed for polyethylene, such as molding, extrusion into fiber or pipe and in the coating of wire and other substrates.

Although the blends of the present invention are illustrated as three component blends, it is to be understood that the illustration is merely of the types of polymeric materials that are employed. Thus, it is feasible to employ two polyethylene components giving rise to a blend having the indicated properties for the polyethylene. Similarly, it is possible to have more than one acid copolymer present in the acid copolymer component of the blend. Additives normally employed with polyethylene, e.g., antioxidant, ultraviolet light stabilizers, slip additives, antistatic agents, pigments, etc., may also be added to the blends of the present invention.

I claim:

1. A blend comprising (a) about 50 to about 90% based on the weight of the blend of random ethylene/ methacrylic acid copolymer in which the acid Constitutes from 2 to mole percent of the copolymer, said random copolymer having a melt index of 0.5 to 50 dg./min., (b) about 5 to about 45% polyethylene having a density of 0.910 to 0.970 g./cc. and a melt index of 0.1 to 20 dg./min. and (c) at least about 5% based on the weight of the blend of ethylene/vinyl acetate copolymer in which the vinyl acetate constitutes from 5 to mole percent of the copolymer, said copolymer having a melt index of 0.5 to dg./min.

2. The blend of claim 1 in the form of a film.

3. The blend of claim 1 having a melt index of about 15 to dg./rnin.

4. The blend of claim 1 in which the polyethylene has a density of 0.945 to 0.970 g./cc. and the polyethylene is present to the extent of between 10 and 20 Weight percent.

References Cited UNITED STATES PATENTS 3,298,855 1/1967 Helin et al. 117-76 3,182,101 5/1965 Rees 260885 3,248,359 4/1966 Maloney 260-41 FOREIGN PATENTS 87,132 9/1964 India.

GEORGE F. LESMES, Primary Examiner.

C. J. SECCURO, Assistant Examiner. 

